The dusting of powders has been a problem since the earliest times. Industrial emphasis on the control of dust began in the early years of the coal and the flour-milling industries where the dust was not only a health hazard, from the point of view of ingestion of the dust by breathing, but an explosion and fire hazard as well. In modern plants, particularly those in which pigments are processed for the paint and plastic industries, and most particularly with respect to those pigments that exhibit high-dusting tendencies, the dust evolved is a constant source of annoyance and danger in the plant. In recent years the necessity of complying with various federal and state regulations in the pollution control area as well as others, has made the provision of suitable dust control means a matter of considerable urgency.
Particularly in the handling of certain metal oxides, such as beryllium and selenium oxides, which are highly toxic and at the same time have an intense proclivity to dust, the elimination of dusting is critical to effect safe handling. Consequently, many attempts have been made to bind the dust in some manner and to control it to some extent. For example, attempts have been made to allay dust by misting water in the air so as to maintain an excess of humidity in the area. Oils have also been used around coal dust to alleviate the problem. Such methods are inapplicable where pigments and other powders are processed by the very requirement that the pigments be dry.
Thus, where dry particulate dusting powders are routinely processed, vacuum systems are used to suck the dust-laden air out to a collection means, such as an air filter, Cottrell precipitator, or the like. In this regard, it might be worth noting that a monumental effort has been directed towards compositions suitable for coating air filters and other dust collection means to entrap dust more effectively and to permit the operation of the dust separation means over relatively long periods of time.
The instant invention is directed to a method for preventing the formation of dust during the processing of finely divided materials, such as pigments, stabilizers, blowing agents, many food substances as well as pharmaceutical materials, thus dispensing with the requirements of complicated and increasingly more sophisticated and expensive dust collection apparatus.
A large volume of prior art is directed to the collection of dust which has been spread over an area, such as sweeping compositions, which are useful for sweeping up layers of dust, and compositions which may be applied to cloths, mops, sponges, and the like, which may be contacted with surfaces on which dust is deposited, thus forcing the dust to adhere to the article impregnated with the composition. The instant invention is directed solely to the prevention of dust in bulk, finely divided and super-finely divided, particulate powders which, having been treated in accordance with the instant process, may be handled freely and spread in relatively thin layers without exhibiting dusting. Materials which exhibit high-dusting are exemplified by finely ground silica of less than 325 Tyler mesh, finely ground pigments, flour, and other materials which have a significant superfines content. Other powders in the sub-micron size which have a high tendency to dust are talc, clay, particulate electro-deposited metals and metal oxides formed in certain processes, and particularly carbon black and various forms of activated carbon.